(těr'ə-sôr') Any of various extinct flying reptiles of the Jurassic and Cretaceous Periods with wings consisting of a flap of skin supported by an elongated fourth digit on each forelimb (rather than an elongated second digit as in birds). Some pterosaurs were unique among reptiles in being covered with hair. Pterosaurs had wingspans ranging from less than 0.3 m (1 ft) to close to 15.2 m (50 ft).